This invention relates to acyclic machines, and more particularly to such machines utilizing a plurality of interleaved rotor disks and stator disks connected in series by liquid metal current collectors providing electrical connection between adjacent rotor and stator disks. This may be a machine of the disk type or of the disk/drum type, the latter being disclosed in U.S. patent application Ser. No. 898,923, filed Apr. 21, 1978, by the instant applicant and assigned to the assignee of the instant application; the disclosure of which is incorporated herein by reference.
In high current, high speed operation of acyclic machines, it is necessary to provide a constant high current capacity contact between rotor and stator disks. In machines using liquid metal current collectors, this requires a constant supply of liquid metal to current collectors in order to continuously wet the contact surfaces between rotor and stator disks. At high speeds of operation, the centrifugal force and Lorentz expulsion forces tend to drive the liquid metal from the inner current collectors. This would result in their operating dry, which would provide an inadequate current carrying capacity for high current density machines, and, therefore, result in severe damage to the current carrying contact surfaces on the current collectors.
Liquid metal circulation means and methods are known in the prior art for circulating metal around a current collector ring. Such a method is disclosed in U.S. Pat. No. 4,027,183 of the instant inventor, issued May 31, 1977 and assigned to the assignee of the instant application. Also in the prior art is a liquid metal current collector of the type disclosed in U.S. Pat. No. 4,027,184, issued May 31, 1977 to Hurley and assigned to the assignee of the instant application. These disclosures are drawn to localized circulation of liquid metal around a single current collector, and require a large quantity of liquid metal within the gap between the stator and the rotor. The large quantity of liquid metal causes large viscous losses due to frictional contact between the rotating rotor surfaces and the liquid metal.
Also known in the prior art is the liquid metal distribution system as disclosed in U.S. Pat. No. 3,211,936, issued Oct. 12, 1965 to Harvey. This patent discloses an external pumping supply system to provide liquid metal to the current collectors. This provided only for liquid metal supply through passages provided external to the apparatus.
Also in the prior art is U.S. Pat. No. 3,989,969, issued Nov. 2, 1976 to the instant applicant and assigned to the instant assignee. That patent discloses a method of liquid metal circulation around an intermediate current collector to provide continuous liquid metal contact between the stator and rotor collector rings, making use of the Lorentz expulsion force to drive the circulation of the liquid metal. This provides only circulation in the vicinity of a single collector ring.
None of the prior art patents discloses a means for or a method of circulating liquid metal entirely through the stator disks. The circulation paths provided by the prior art relied upon external equipment, or provided only localized circulation around a single collector ring.
The primary object of the instant invention is to provide an automatic and reliable supply of liquid metal from the region adjacent an outer current collector of an acyclic machine to the region adjacent an inner current collector at all speeds of operation in both directions of rotation. A second object is to accomplish this supply of liquid metal while employing a minimum quantity of the liquid metal in each current collector site, so as to reduce to a minimum the viscous drag losses of operation at high rotational speed.